1. Field of the Invention
The present invention relates to a washing machine, and more particularly, to a method and an apparatus for sensing a level of water supplied in washing tub of the washing machine.
2. Prior Art
In order to determine a water level suitable for washing laundry articles, a water level sensing operation is preferably carried out before performing a washing operation in a washing machine. Generally, the water level sensing operation includes a dry load sensing method which senses washing loads in a dry state without supplying water and a wet load sensing method which senses washing loads in a wet state after supplying water.
U.S. Pat. No. 5,419,163, (issued to Jung H. Kim et al. on May 30, 1995) discloses an apparatus for controlling a washer based on an amount of a washing water, a polluted degree of the washing water, an amount of clothes to be washed, a detergent, and etc.
FIG. 1 illustrates a conventional water level sensing apparatus in a washing machine. The conventional water level sensing apparatus includes a load sensor 102, a water supply section 104, and a microprocessor 106. The load sensor 102 senses a weight of a dry load or a wet load supplied in washing tub 100 of the washing machine under the control of the microprocessor 106. The weight of the dry load or wet load is fed to the microprocessor. The water supply section 104 supplies the washing tub 100 with water under the control of the microprocessor 106. The microprocessor 106 determines a water level based on the weight of the dry load from the load sensor 102. The microprocessor 106 also judges whether or not the water supplied in washing tub 100 has reached the water level determined.
FIG. 2 illustrates a conventional water level sensing method in a washing machine by a dry load sensing manner. In step S201, a load sensor 102 senses a weight of a dry load supplied in washing tub 100 of the washing machine under the control of the microprocessor 106. The weight of the dry load is supplied to the microprocessor 106. The microprocessor 106 receives the weight of the dry load from the load sensor 102 and determines a water level based on the weight of the dry load(step S202).
In step S203, the water supply section 104 starts to supply the washing tub 100 with water under the control of the microprocessor 106. In step S204, the microprocessor 206 judges whether or not the water supplied in washing tub 100 has reached the water level determined in step S202. As a result of the judgement in step S204, when the water supplied in washing tub 100 has not reached the water level determined in step 202, the routine returns to step S203. When it is judged that the water supplied in washing tub 100 has reached the water level determined in step 202, the microprocessor 106 performs a washing operation(step S205).
FIG. 3 is a flow chart for illustrating a conventional water level sensing method in a washing machine by a wet load sensing manner. In step S301, the water supply section 204 starts to supply the washing tub 100 with water under the control of the microprocessor 106. In step S302, the microprocessor 106 judges whether or not the water supplied in washing tub 100 has reached a lowest water level.
As a result of the judgement in step S302, when the water supplied in washing tub 100 has not reached the lowest water level, the routine returns to step S301. When it is judged that the water supplied in washing tub 100 has reached the lowest water level, the load sensor 102 senses a weight of a wet load supplied in washing tub 100 under the control of the microprocessor 106. The weight of the wet load is applied to the microprocessor 106. The microprocessor 106 receives the weight of the wet load from the load sensor 102 and determines a water level based on the weight of the wet load(step S304). In step S305, the water supply section 204 supplies the washing tub 100 with water to the water level determined in step S304 to thereby complete the water supply. Then, the microprocessor 106 performs a washing operation(step S306).
In a conventional water level sensing method in a washing machine, one of a method for sensing loads in dry and wet states is achieved. Therefore, difference between load sensing in dry and wet states greatly occurs. For example, laundry such as a coverlet or a woolen jacket is light in a dry state but heavy in a wet state. Thus, even if sensing a water level with respect to the coverlet or woolen jacket in the wet state is exact, sensing a water level with respect to the coverlet or woolen jacket in the dry state occurs great error.